In a 4- to 5-quart slow cooker, layer sweet peppers, celery, and onion. Season chops with garlic salt and black pepper. In a very large skillet, heat oil over medium heat. Cook chops, half at a time, until brown on both sides. Add chops to cooker. In a small bowl combine broth, orange juice, chipotle peppers, and oregano. Pour over chops in cooker. Cover, cook on low setting for 6 to 7 hours or on high setting for 3 to 3 1/2 hours. Using a slotted spoon, transfer chops and vegetables to a platter, discarding cooking liquid.